Election posters of the right-wing Alternative for Germany (AfD) and Social Democratic Party (SPD) are seen in Greifswald, Mecklenburg-West Pomerania, Germany August 30, 2016. REUTERS/Stefanie Loos

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BERLIN (Reuters) - The anti-immigrant Alternative for Germany (AfD) has overtaken Chancellor Angela Merkel's conservative Christian Democrats (CDU) in a pre-election poll in the eastern state of Mecklenburg-Vorpommern, Cicero magazine said on Wednesday.

The poll, conducted by the Insa Institute for the monthly Cicero, forecast the AfD would win 23 percent of the vote in Sunday's state election, compared to 20 percent for the CDU, which would mark a huge setback for Merkel in her home state.

"It would be a complete meltdown for the Christian Democratic Union if a new party was able to establish itself on a statewide level to the right of the Union, and actually exceed its size," Cicero wrote on its website.

Germany remains deeply unsettled, with anti-immigrant sentiment rising, after 15 people were killed and dozens wounded in five separate attacks between July 18 and 26. Two attacks were claimed by Islamic State militants, and three of the assailants were asylum seekers.

Critics have seized on the attacks to criticize Merkel's open-door refugee policy, under which hundreds of thousands of migrants, many fleeing war in Afghanistan, Syria and Iraq, entered Germany in the past year.

Cicero's poll showed the left-leaning Social Democrats (SPD), part of Merkel's ruling coalition in Berlin, led in Mecklenburg-Vorpommern with 28 percent of the vote. The SPD heads the state's current governing coalition.

The latest polling results would allow the current SPD-CDU coalition government to continue to govern the northeastern state, with a combined 48 percent of the projected vote.

It could also enable a governing combination of the leftist Linke party, which is projected to get 15 percent of the vote in Sunday's election, together with the SPD and the Green party, which is projected to get 6 percent of the vote.

All the parties now represented in the state parliament have ruled out forming any coalition with the AfD.